Normal Summon "Koa'ki Meiru Doom". Then use "Gallis"'s effect, dealing damage and Special Summoning it. The when both of them are on the fied, activate the effect of Birdman from your hand by returning Gallis to your hand as a cost. "Koa'ki Meiru Doom" negates the activated effects of LIGHT and DARK monster (without destroying them), so Birdman stays in hand. Activate the effect of Gallis (which summons itself while dealing damage) and repeat using Birdman to recycle Gallis. "Koa'ki Meiru Doom" simply needs to stay on the field.